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The for equipment system of the complex network of command system of special structure and function, respectively from unit layer, sub network layer and network layer extraction reliability evaluation parameters, based on sub network efficiency established perception subnet, accused of subnet and combat the reliability index of the network and maintenance network, and each sub network reliability evaluation model are established using the network analysis method.

Single crystal of the Sc2Si2O7:Ce (SPS:Ce) was grown by floating zone method. The crystal structure is confirmed to be thortveitite with space group C2/m by X-ray diffraction measurement. The vacuum ultra violet (VUV), photoluminescence excitation (PLE) and photoluminescence (PL) spectra, fluorescence decay time and X-ray excited luminescence spectra were studied. Five sublevels of Ce3+ 5d level are observed through the VUV PLE spectra. The PL is dominated by the fast Ce3+ 5d14f0–5d04f1 transition peaking at 386 nm with a single exponential decay of 33 ns. The traps in SPS:Ce were also studied through the thermally stimulated luminescence measurement. A trap with level depth 1.16 eV with a kinetics order of 1.52 is found in the SPS:Ce crystal.

The emission properties of Eu 2+ and Mn 2+ in monoclinic SrAl 2 Si 2 O 8 (M-SAS) and hexagonal BaAl 2 Si 2 O 8 (H-BAS), both of which have only one alkaline-earth site, were studied. The emission peaks of both Eu 2+ (405 nm) and Mn 2+ (564 nm) in SrAl 2 Si 2 O 8 , are located at longer wavelengths, compared with those in H-BAS (373 nm for Eu 2+ and 518 nm for Mn 2+ ), because of the stronger crystal field strength at the Sr site. EPR spectra showed that the g values of Mn 2+ are 4.5065 in M-SAS:Mn and 2.0247 in H-BAS:Mn. Magnetic measurements proved that Mn 2+ was at high-spin state in both hosts. The large g value of Mn 2+ in M-SAS was ascribed to the mixing of the first excitation state to the ground state, both of which have lower d orbital degeneracy due to the lower symmetry of Mn 2+ site. The transfer efficiency from Eu 2+ to Mn 2+ was about 10% in M-SAS, higher than that in H-BAS (5%). This was probably because Eu 2+ emission overlaps the relatively low excitation level of Mn 2+ in M-SAS. In order to obtain high transfer efficiency, it was necessary for the Eu 2+ emission to overlap the lowest excitation level of Mn 2+ . The results obtained in this work may be helpful to design the new white or red phosphors for white-light emitting diode (w-LED) applications.

A coating method with precipitating process was developed to reduce the particle size and to improve the particle dispersion of Y3Al5O12:Tb3+ phosphor prepared by sol–gel method. The particle morphology was observed by using SEM and TEM; and the particle size and its dispersion was measured by using laser scattering technique. Several coating materials were tested. Among them, Al2(SiO3)3 coating not only reduced the particle size from several micrometers to ∼1 μm and improved the particle dispersion, but also well kept luminescent intensities and improved the duration of the phosphor under the bombardment of cathode ray. The mechanism of the particle size reduction was proposed.

The phosphors in the system Sr 2− x − y P 2 O 7 : x Eu 2+ , y Mn 2+ were synthesized by solid-state reactions and their photoluminescence properties were investigated. These phosphors have strong absorption in the near UV region, which is suitable for excitation of ultraviolet light emitting diodes (UVLEDs). The orange-reddish emission of Mn 2+ in these phosphors can be used as a red component in the tri-color system and may be enhanced by adjusting the Mn 2+ /Eu 2+ ratio. The energy transfer from Eu 2+ to Mn 2+ is observed with a transfer efficiency of ∼0.45 and a critical distance of ∼10 A. The results reveal that Sr 2− x − y P 2 O 7 : x Eu 2+ , y Mn 2+ phosphors could be used in white light UVLEDs.

The photochemical and photophysical properties of the three C121 isomers (I, II, III) were investigated with MADLI-TOF-MS, UV-vis spectra, fluorescence spectra, absorption spectra of their DMA complexes, and theoretical calculations. The three isomers of C121 (I, II, III) have different stabilities under laser irradiation, but isomer I and isomer II show good stability against the heat-induced conversion between different isomers: No conversion between the isomers was found after heating the mixture of isomer I and isomer II at 353 K for 12 h in Ar atmosphere. The results of UV-vis absorption and fluorescence spectra indicate that interactions between two C60 moieties of C60=C=C60 in the ground and singlet states are not significant, C121 (I, II, III) behaves as an electron-acceptor similar to C60. These indicate that the formation of the fullerene chain structure (e.g., C60=C=C60) does not disturb the photochemical and photophysical properties of the C60 monomer itself, even that the properties were enhanced by the formation of the polymer. This is significant for the C60 polymer in photochemical or photoelectronic applications in which C60=C=C60 can be an excellent basic unit of polymers.

DC resistivity, dielectric constant, dielectric loss and positron annihilation spectra of (Ba1−xHox)TiO3 ceramics have been measured as a function of holmium concentration x. It has been found that the DC resistivity of (Ba1−xHox)TiO3 is strongly dependent on the Ho content: it decreases three orders of magnitude and reaches a minimum at x = 0.4%. Doping with 0.6% holmium increases the permittivity of BaTiO3 by approximately three times (from ∼1,300 to ∼4,000), with only a slight increase in the corresponding dielectric loss. The local electron density and defect concentration estimated using positron annihilation technique conforms well to the features found in the dielectric and resistivity measurements. The results have been discussed in terms of a mixed compensation model.

ZnO phosphor was synthesized by annealing ZnO powder at low O2 partial pressure and in vacuum. ZnO has two emissions, which are located at about 380 nm (UV emission) and 510 nm (green emission). The UV emission can be attributed to the exciton emission, which is a single-center process, whereas the green emission is related to native defects, such as V•O and V′Zn, which is a two-center (donor-acceptor) recombination process. The high-density excitation favors the UV emission, whereas the green emission likely appears in the samples annealed at low O2 partial pressure. It was shown that the energy transfer may occur from the UV emission center to the green emission center, and the exciton diffusion mechanism for the transfer was proposed.

Wuhan Univ, Dept Phys, Wuhan 430072, Peoples R China. Chinese Acad Sci, Int Ctr Mat Phys, Shenyang 110016, Peoples R China. Wuhan Univ, Ctr Electron Microscopy, Wuhan 430072, Peoples R China.;Shi, J (reprint author), Wuhan Univ, Dept Phys, Wuhan 430072, Peoples R China;jshi@whu.edu.cn

A new kind of photodegradable polystyrene (PS)–TiO 2 nanocomposite film was synthesized. The TiO 2 nanoparticles were first modified by grafting polymer on its surface (G-TiO 2 ), and then the PS–G-TiO 2 composite films were formed through polymerization. The photocatalytic degradation of the composite films was investigated. The as-prepared films were characterized by scanning electron microscope (SEM), gel permeation chromatogram (GPC), FT-IR and UV-Vis spectroscopy, and the photoinduced weight-loss. The results show that PS–G-TiO 2 nanocomposite films could be efficiently photocatalytically degraded under UV illumination in air. The weight-loss of the PS–G-TiO 2 film reached 29%; the average molecular weight reduced to 1/4 of the original molecular weight under UV-light irradiation for 300 h, implying that some benzene rings had been cleaved. The photocatalytic degradation mechanism of the films is briefly discussed.

A combined electric field and near-field scanning optical microscope (EF-NSOM) system has been developed for imaging and modifying surfaces. With a negative bias applied to the conducting scaling probe with respect to the substrate, the EF-NSOM system is used to modify nearly atomically flat n-type oxide-passivated Si( 111) surfaces. The electric-field-induced modification of Si surfaces, similar to that effected by a scanning tunneling microscope or an atomic force microscope, is observed by the near-field scanning optical microscopy as well as by shear-force microseopy.

An azobenzene self-assembled monolayer (SAM) was used to obtain the two-dimensional surface-enhanced Raman scattering (SERS) maps of gold substrates, which were prepared by electrochemical roughening and colloidal Au nanoparticle assembling, respectively. The Raman maps thus obtained showed that the lateral distribution of SERS intensity varies to a significant extent over the substrate surface. Especially, the nanoparticle substrate has a more homogeneous distribution of SERS enhancement factors than that of the electrochemically roughened one, which are believed to reflect the different morphology of these two substrates.

Based on photoluminescence, Fourier transform infrared spectroscopy, and atomic force microscopy results, a new light emitting model for porous silicon (multiple source quantum well model) is proposed.

powder samples are prepared by high-temperature solid-state reactions and the as-produced samples are annealed in various atmospheres with different , partial pressures, such as vacuum, , and , as well as Mg and Ga metal atmospheres. After annealed in the atmospheres with low partial pressures, the samples give bright blue luminescence with the main peak at and peak width (full width at half maximum) . Based on the photoluminescence (PL) spectra, PL decay curve, and electron paramagnetic resonance spectra, as well as the defect equilibrium analysis, the PL mechanism of donor–acceptor recombination is proposed, in which is assigned as the donor and is assigned as the acceptor. The PL intensity of is comparable with the commercial ZnO phosphor.

Pure phase Zn 2 GeO 4 was fabricated by solid state reactions and the products were annealed in various atmospheres, such as O 2 , air, N 2 , vacuum, Zn, and Ge. The material was a native defect phosphor presenting white-bluish emission and its photoluminescence was about 40% brighter than that of the commercial ZnO phosphor. The electron paramagnetic resonance (EPR) measurements showed the existence of Zn; (or Zn + ), an abnormal valence for Zn. Additionally, V o , V zn, and ionized V Ge were also detected by EPR. The model for the luminescent emission of this native defect phosphor was proposed, which may arise from the recombination between the donors (V o and Zn,) and the acceptors (V' zn and ionized V Ge ).

β-Ga 2 O 3 , a native defect luminescent material with blue emission, was fabricated by annealing β-Ga 2 O 3 powders under various O 2 partial pressures or in Ga metal atmosphere. Annealing under low O 2 partial pressure favors the photoluminescence (PL), which indicates that V X o should be one of the luminescence centers in this phosphor. Annealing in Ga metal atmosphere reduced the PL intensity, which indirectly suggests that VX Ga or defect cluster (V Ga, V o ) X might be another luminescent center. Electron paramagnetic resonance (EPR) measurements verified the existence of single ionized oxygen vacancy (V o ). An EPR signal with g = 4.0468 and four hyperfine lines was observed, which is considered to be related to Ga 2+ and the hyperfine interaction parameter is 112 G. Furthermore, the correlations between PL intensity and the densities of V o as well as Ga 2+ were studied. At present, although we can not clarify whether Ga 2+ exists as Ga¨ i or Ga' Ga , V X o , and Ga 2+ may act as donors, whereas VX Ga or (V Ga, Vo) X may act as accepters for the luminescence.

The influence of low-pressure O2 and Zn atmosphere on the luminescent properties of ZnO phosphor was investigated. The intensity of the green emission of ZnO phosphor was enhanced when the samples were annealed in low-pressure O2, whereas Zn atmosphere annealing reduced the emission intensity. The equilibrium analysis of native defects supported that a donor‐acceptor recombination process may be applied to the green emission, in which oxygen vacancy and Zn vacancy played the roles of the donor and the acceptor, respectively. The existence of VO